The present invention relates to a magneto-optical recording medium for use as a magneto-optical memory, a magnetic recording and display element and so forth and, more particularly, to a magnetic thin film recording medium which has an easy axis of magnetization in a direction perpendicular to the film surface and permits recording of information by forming an inverted magnetic domain of a cylindrical or any other arbitrary configuration and reproducing of the information through utilization of the magnetic Kerr effect.
With ferromagnetic thin films which have an easy axis of magnetization in a direction perpendicular to their film surface, it is possible to form a small inverted magnetic domain of a magnetic polarity reverse from a uniform magnetization polarity in the film surface uniformly magnetized to a south or north magnetic pole. By making the presence and absence of such inverted magnetic domains correspond to digital signals "1" and "0", respectively, such ferromagnetic thin films can be used as high density magnetic recording media. These ferromagnetic, vertically magnetized thin films are typically amorphous rare earth, transition metal alloy thin films, such as, for example, Gd-Co, Gd-Fe, Tb-Fe, Dy-Fe, GdTbFe, etc.; in addition, there are MnBi as a polycrystalline metal thin film and GIG as a compound single crystal thin film.
Recording of information in these thin films is usually effected by heating them up to a temperature higher than the Curie temperature or magnetic compensation temperature of the thin films to form therein an inverted magnetic domain at a desired position. The recorded information is reproduced through utilization of the magnetic Kerr effect that when linearly polarized light is incident on and reflected by the magnetic thin film, the plane of polarization rotates to the right or left according to the direction of magnetization (the Kerr rotation).
In this case, the S/N ratio obtained by reading out a recorded signal by means of light is not so high.